Author Topic: Engine idles low after warm up. 1985 B250 w/318  (Read 472 times)

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Offline justin2576

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Engine idles low after warm up. 1985 B250 w/318
« on: August 1, 2020, 07:00:09 pm »
I have been trying to diagnose a low idle issue in my 1985 B250 van.  It idles normal, or maybe even a little high during warm up, then after its warmed up the RPMs drop and it idles low and runs rough.  It dies when I put it in gear, so I have to hit the gas and brake at stoplights.  I have replaced plugs, wires, dist. cap & rotor, and coil.  Recently replaced the EGR Valve.  Sometimes it runs normal, then after a few minutes I hear it bog down and idle rough.  Most times it just runs rough right after it warms up.

Not sure if its related, but sometimes it even runs really bad like its missing a plug wire, but that only happens once in a while.  I have not adjusted the carb yet.  It has a Holley 2280, and only 1 adjusting screw.  The idle seems to be adjusted by some kind of electric solenoid.

What should I check next?  Thanks.


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    Offline Mighty Quinn

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #1 on: August 1, 2020, 10:22:43 pm »
    Sounds like it is running lean (not enough fuel) once warmed up. It is a two barrel carb so there should be two idle mixture adjustment screws. You need to google Holley 2280 and look at the Holley diagram. you will see the adjustment screws on each side of a purge port.near the base of the carb. There is a seperate idle set rpm screw once you get the mix right. Its all on the diagram. Good luck!
    1976 W100 Adventurer Sport, standard cab,Sweptline short bed,400,np435 354/355 Dana 44FBJ/9.25
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    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #2 on: August 2, 2020, 02:04:48 am »
    Thanks for the info.  I have not been able to find the idle adjustment screws. Is it possible that they are hidden or plugged or something?  Also, is it possible the gas could be affecting it? I've been putting premium in since it's an older engine, but all gas stations around me has 10% ethanol in it.

    Offline DODGEBOYS

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #3 on: August 2, 2020, 12:27:44 pm »
    email me [ its below] for either the BBD or 2280 adjustment diagram , do you know if you have a Carter or Holley Carb
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
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    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #4 on: August 2, 2020, 02:42:16 pm »
    DODGEBOYS, I just sent you an e-mail
    I don't know what BBD is, but the adjustment diagram would be helpful.  Thanks.  I have been searching the web for more information on it.

    I believe I have a Holley 2280.  Here are the ID numbers:
    R 40165 1
    4306465
    0845

    It looks pretty dirty on the outside, but the inside looks clean.  Not sure if its time for a re-build yet, but it's the original since 1985, so probably wouldn't hurt.

    The picture of the carburetor is taken from the driver's seat behind the engine and looking forward to the front.  You can see there is only one adjustment screw.  The throttle seems to be adjusted from the solenoid on the left (drivers side).

    Offline Mighty Quinn

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #5 on: August 2, 2020, 09:35:52 pm »
    That dosen't look like a Holley, Must be the Carter BBD DODGEBOYS is talking about. Forget everything I told you and DODGEBOYS will get you straightened out.
    1976 W100 Adventurer Sport, standard cab,Sweptline short bed,400,np435 354/355 Dana 44FBJ/9.25
    1978 AW100 RC Custom 440,8 track
    2018 Ram 2500 HD Tradesman 6.4 Hemi

    Offline DODGEBOYS

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #6 on: August 3, 2020, 09:06:38 am »
    he has the Holley and thats the info l sent him
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
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    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #7 on: August 3, 2020, 10:38:12 am »
    Here is a pic of the other side of the solenoid.  It has a spring and a screw.  According to the FSM I need to remove the spring and screw to adjust:

    "d.   Remove adjusting screw and spring from solenoid, then insert a 1/8 inch allen wrench into the solenoid and adjust to correct engine RPM."

    Should I adjust this BEFORE messing with the idle mixture screws?

    Offline DODGEBOYS

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #8 on: August 3, 2020, 12:02:33 pm »
    thats the HIGH idle adjustment / the LOW idle adjustment [ what you want ] is just turn the screw IN to raise BASE idle
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
    [email protected]
    former Parts Mgr & A1 Tech @ Pete's Chrysler -Plymouth
    DO NOT use the site IM,s to contact me  l have them turned OFF

    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #9 on: August 3, 2020, 04:07:46 pm »
    Should the adjustment screw always be hitting the fast idle cam?  After the engine is warmed up that cam falls down really low and the screw isn't touching anything, so turning it wouldn't really do anything.  Perhaps that's the problem.

    Offline dodge82273

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #10 on: August 3, 2020, 04:29:11 pm »
    the fast idle cam ... its screw you have pictured in your first pix , ounce its warm YES it's suppose to fall way down , that screw NO longer doing anything , its just for cold / choke idle speed .
     the solenoid , the screw you see , is the base dodgeboys is talking about , your book is talking about the HIGH idle setting . what should happen with that solenoid is this , key on engine running WARM , electric makes it pop out and hold the idle at say 725 rpm +/- when you switch key to OFF that solenoid is de energized and drops back closing the carb ALL the way , this prevents whats called run-on or dieseling by shutting off all air to motor . Because yours runs , but slow , its presumed that solenoid is working but the base rpm needs to be raised , do as suggested , if it the diesels , check to see if that solenoid pops out , goes + back , key on / note you MAY have to step on the gas a tad to remove return spring pressure from it if its weak .. set well that solenoid isn't required , older units did not have them at all .
    78 to 93 parts trucks
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    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
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    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #11 on: August 3, 2020, 04:42:54 pm »
    I have never seen that solenoid move.  Unless the movement is too small for me to see.  I will start the engine and warm it up and see if I see any movement.  Maybe the solenoid is not functioning.  Is there a way to test it?

    Offline DODGEBOYS

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #12 on: August 3, 2020, 07:53:53 pm »
    I have never seen that solenoid move.  Unless the movement is too small for me to see.  I will start the engine and warm it up and see if I see any movement.  Maybe the solenoid is not functioning.  Is there a way to test it?

    the test is right in the FSM on setting the idle = NOW dont tell me you have a HAYNES or Chiltons manual and NOT a REAL - FSM
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
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    DO NOT use the site IM,s to contact me  l have them turned OFF

    Offline justin2576

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #13 on: August 4, 2020, 02:16:04 am »
    I have the FSM but I just missed this one completely.  Most of the references to the carb show the two screws and not the solenoid, so I skipped out on some reading.  I found the section for adjusting the idle.  I disconnected the lead wire from the solenoid and ran a jumper wire to the positive terminal on the battery.  I got a little bit of a spark, so it seems that I'm drawing some current, but the solenoid does not move at all.

    I fired the engine up today and noticed that after its warmed up the solenoid isn't even touching the linkage on the throttle body assy.  I can slip a thin piece of cardboard between the linkage and the end of the solenoid.  I think the only thing keeping the engine idling is the limits of the linkage itself. 

    Replacing the solenoid will be my next step.

    Offline dodge82273

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #14 on: August 4, 2020, 03:06:21 am »
    try cleaning / lube it ...
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Jeffy45

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #15 on: August 4, 2020, 04:22:40 am »
    Think i asked this before. Isnt the AC ( accesory) solinoid there for when you turn the ac on. The compressor turns on, the vaccume drops ,the RPM's drop, the solinoid ( throttle kicker) energizes and jumps the idle back up where its supposed to be??
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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #16 on: August 4, 2020, 10:36:18 am »
    Think i asked this before. Isnt the AC ( accesory) solinoid there for when you turn the ac on. The compressor turns on, the vaccume drops ,the RPM's drop, the solinoid ( throttle kicker) energizes and jumps the idle back up where its supposed to be??

    yes you are right to a point , but the throttle kicker also sets BASE idle / if you look at his Carb and read a FSM it shows that where a normal Carb would have a base idle screw its missing because the throttle kick does that job / see my post # 6 above and the picture
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
    [email protected]
    former Parts Mgr & A1 Tech @ Pete's Chrysler -Plymouth
    DO NOT use the site IM,s to contact me  l have them turned OFF

    Offline DODGEBOYS

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #17 on: August 4, 2020, 10:38:57 am »

    I fired the engine up today and noticed that after its warmed up the solenoid isn't even touching the linkage on the throttle body assy.  I can slip a thin piece of cardboard between the linkage and the end of the solenoid.  I think the only thing keeping the engine idling is the limits of the linkage itself. 

    Replacing the solenoid will be my next step.

    the solenoid should be contacting the throttle linkage , thats what controls base idle
    put your truck info HERE
    MOPAR TO YA!!!!!! AARON HOWORD TOWNSEND / SLANTEDMIND---GOD BLESSDODGEBOYS FSM STORE
    [email protected]
    former Parts Mgr & A1 Tech @ Pete's Chrysler -Plymouth
    DO NOT use the site IM,s to contact me  l have them turned OFF

    Offline Jeffy45

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    Re: Engine idles low after warm up. 1985 B250 w/318
    « Reply #18 on: August 4, 2020, 12:04:42 pm »
    Copy that👍
    1988 Ramcharger LE 150 318 TBI 727 non-lockup.                   
           " If a law is unjust, a man is not only right to disobey it,   
                    he is obligated to do so"                                                   
                                                                 - Thomas Jefferson